Overload protective apparatus of a compressor and a method thereof

ABSTRACT

In an overload protective apparatus of a compressor and its method capable of preventing damage of a compressor due to overload by removing an overload protector and using an operation control device operating the compressor, the overload protective apparatus includes a reference current setting unit for presetting a reference current value for operating the compressor normally; a microcomputer for generating a power cutoff signal when the detected current value is greater than the reference current value and generating a power supply signal when the detected current value is smaller than the reference current value; and a power supply unit for cutting off power applied to the compressor on the basis of the power cutoff signal or applying power to the compressor on the basis of the power supply signal.

TECHNICAL FIELD

The present invention relates to a compressor, and particularly, to anoverload protective apparatus of a compressor and its method capable ofpreventing a compressor for being damaged by overload without using anover load protector (OLP).

BACKGROUND ART

In general, a compressor, particularly, a reciprocating compressor hasno crankshaft for converting a rotating movement to a linear movement,thereby having small friction loss and so having higher efficiency incompression than that of a general compressor.

In case that the reciprocating compressor is used for a refrigerator oran air conditioner, as a stroke voltage inputted to the reciprocatingcompressor is varied, a compression ratio of the reciprocatingcompressor can be varied to control freezing compressor. Such areciprocating compressor will now be described with reference to FIG. 1.

FIG. 1 is a block diagram showing a structure of an operation controldevice of the reciprocating compressor in accordance with theconventional art.

As shown therein, the operation control device of the reciprocatingcompressor includes: a voltage detecting unit 14 for detecting a voltageapplied to the reciprocating compressor 13 as the compressor operates; acurrent detecting unit 12 for detecting a current applied to thereciprocating compressor 13 as the compressor operates; a microcomputer15 for calculating a stroke by using the voltage detected by the voltagedetecting unit 14 and the current detected by the current detecting unit12, comparing the calculated stroke and a stroke reference value, andoutputting a switching control signal on the basis of the comparisonresult; and a power supply unit 11 for supplying a stroke voltage to thereciprocating compressor 13 by on-off controlling AC power supplied tothe reciprocating compressor 13 according to the switching controlsignal outputted from the microcomputer 15 by using an internal triac(Tr1). Herein, the reciprocating compressor 13 receives a stroke voltageprovided to an internal motor (not shown) according to a strokereference value set by a user and varies an internal stroke so as tovertically move a piston (not shown) in the compressor.

Hereinafter, operations of the operation control device of areciprocating motor compressor in accordance with the conventional artwill now be described.

First, the reciprocating motor compressor 13 receives a voltage suppliedto the motor on the basis of the stroke reference value set by a userand varies the stroke so as to vertically move the stroke. Herein, thestroke means a moving distance of a piston in the reciprocating motorcompressor 13 in a reciprocating movement.

A turn-on period of the triac (Tr1) of the power supply unit 11 islengthened by a switching control signal outputted from themicrocomputer 15. As the turn-on period is lengthened, the AC power issupplied to the reciprocating motor compressor 13 to drive thereciprocating motor compressor 13. At this time, the voltage detectingunit 14 and the current detecting unit 12 detect a voltage and a currentapplied to the reciprocating motor compressor 13 and output the detectedvoltage and current to the microcomputer 15, respectively.

The microcomputer 15 calculates a stroke by using the voltage and thecurrent detected by the voltage detecting unit 14 and the currentdetecting unit 12, then, compares the calculated stroke with the strokereference value, and outputs a switching control signal according to thecomparison result. That is, when the calculated stroke is smaller thanthe stroke reference value, the microcomputer 15 outputs a switchingcontrol signal for lengthening an on-period of the triac (Tr1) to thepower supply unit 11 thereby increasing a stroke voltage supplied to thereciprocating motor compressor 13.

On the other hand, when the calculated stroke is greater than the strokereference value, the microcomputer 15 outputs a switching control signalfor shortening an on-period of the triac (Tr1) to the power supply unit11 thereby decreasing a stroke voltage supplied to the reciprocatingmotor compressor 13.

In the conventional art, an over load protector (OLP) 20 for cutting offpower applied to. a motor of the compressor 13 when a temperature of thecompressor 13 is high or when over current flows in a internal motor ofthe compressor 13, is installed independent of the operation controldevice.

Hereinafter, an over load protector (OLP) in accordance with theconventional art will now be described.

The over load protector 20 detects a temperature of a compressor 13electrically connected with itself. In addition, the over load protector20 detects heat due to a current flowing therein, and cuts off or passespower applied to an internal motor of the compressor 13 on the basis ofa temperature of the detected heat. That is, when a temperature of thecompressor 13 gets high, or over current flows in the internal motor ofthe compressor 13, the over load protector 20 operates to cut off powersupplied to the compressor 13, and thus prevents damage of thecompressor 13.

However, the over load protector installed in the compressor 13 inaccordance with the conventional art cannot be minimized by a size of apower device (not shown) in the over load protector 20, and also, a costfor the compressor increases by installing the over load protector inthe compressor.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to provide anoverload protective apparatus and its method capable of preventingdamage of a compressor due to overload by using an operation controldevice operating the compressor without using the overload protector.

To achieve the above object, there is provided an overload protectiveapparatus of a compressor including: a reference current setting unitfor presetting a reference current value for normally operating acompressor; a current detecting unit for detecting a current applied tothe compressor; a microcomputer for generating a power cutoff signalwhen the detected current value is greater than the reference currentvalue, and for generating a power supply signal when the detectedcurrent value is smaller than the reference current value; and a powersupply unit for cutting off power applied to the compressor on the basisof the power cutoff signal, or for applying power to the compressor onthe basis of the power supply signal.

To achieve the above object, there is provided an operation controldevice of a compressor including a voltage detecting unit for detectinga voltage applied to a compressor; a current detecting unit fordetecting a current applied to the compressor; a microcomputer forcalculating a stroke by using a voltage detected by the voltagedetecting unit and a current detected by the current detecting unit,comparing the calculated stroke and a stroke reference value andoutputting a switching control signal on the basis of the comparisonresult; and a power supply unit for supplying a stroke voltage to thecompressor by on-off controlling AC power supplied to the compressor onthe basis of the switching control signal outputted from themicrocomputer by using an internal triac (Tr1), further comprising: areference current setting unit for presetting a reference current valueof the compressor; a microcomputer for generating a power cutoff signalwhen the detected current value is greater than the reference currentvalue and outputting the generated power cutoff signal or for generatinga power supply signal when the detected current value is smaller thanthe reference current value and outputting the generated power supplysignal; and a switching unit for cutting off power applied to theinternal motor of the compressor on the basis of the power cutoffsignal, or for applying power to the internal motor of the compressor onthe basis of the power supply signal.

To achieve the above object, there is provided a method for protecting acompressor from overload comprising: detecting a current applied to acompressor; comparing the detected current value and a pre-storedreference current value; generating a power cutoff signal when thedetected current value is greater than the reference current value, andgenerating a power supply signal when the detected current value is thesame as or smaller than the reference current value; and cutting offpower applied to an internal motor of the compressor on the basis of thepower cutoff signal or applying power to the internal motor of thecompressor on the basis of the power supply signal.

To achieve the above object, there is provided a method for controllingoperation of a compressor including detecting a voltage and a currentapplied to a compressor; calculating a stroke by using the voltage andthe current; comparing the calculated stroke and a stroke referencevalue; and controlling an operation of the compressor on the basis ofthe comparison result, further comprising: comparing the detectedcurrent value and a pre-stored reference current value; generating apower cutoff signal when the detected current value is greater than thereference current value, and generating a power supply signal when thedetected current value is the same as or smaller than the referencecurrent value; and cutting off power applied to an internal motor of thecompressor on the basis of the power cutoff signal, or applying power tothe internal motor of the compressor on the basis of the power supplysignal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a structure of an operation controldevice of a reciprocating compressor in accordance with the conventionalart;

FIG. 2 is a block diagram showing a structure of an operation controldevice and an overload protective apparatus of a reciprocatingcompressor in accordance with the present invention;

FIG. 3 is a block diagram showing a structure of a different embodimentof an overload protective apparatus of a reciprocating compressor inaccordance with the present invention; and

FIG. 4 is a flow chart showing an operational order of an overloadprotective apparatus of a reciprocating compressor in accordance with adifferent embodiment of the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

Hereinafter, there will be described in detail with reference to FIGS. 2through 4, a preferred embodiment of an overload protective apparatusand its method capable of preventing damage of a compressor due tooverload, by using an operation control apparatus for controlling anoperation of the compressor, without using an over load protector.

FIG. 2 is a block diagram showing a structure of an operation controldevice and an overload protective apparatus of a reciprocatingcompressor in accordance with the present invention.

As shown therein, an operation control device of the reciprocatingcompressor includes: a voltage detecting unit 104 for detecting avoltage applied to the reciprocating compressor 103 as a piston in thereciprocating compressor is driven; a current detecting unit 102 fordetecting a current applied to the reciprocating compressor 103 as apiston in the compressor is driven; a microcomputer 105 for calculatinga stroke by using the voltage detected by the voltage detecting unit 104and the current detected by the current detecting unit 102, comparingthe calculated stroke and a stroke reference value, and outputting aswitching control signal on the basis of the comparison result; and apower supply unit 101 for supplying a stroke voltage to thereciprocating compressor 103 by turning on/off AC power supplied to thereciprocating compressor 103 according to a switching control signaloutputted from the microcomputer 105 by using an internal triac (Tr1).

In addition, the overload protective apparatus in accordance with thepresent invention includes: the current detecting unit 102, themicrocomputer 105, the power supply unit 101 and a reference currentsetting unit 106 for presetting a reference current for normallyoperating a motor in the compressor. Herein, when a detected currentvalue is greater than the reference current value, the microcomputer 105generates a power cutoff signal and outputs the generated power cutoffsignal, when the detected current value is smaller than the referencecurrent value, the microcomputer 105 generates a power supply signal andoutputs the generated power supply signal. In addition, the power supplyunit 101, cuts off power applied to an internal motor of the compressor103 on the basis of the power cutoff signal, or applies power to theinternal motor of the compressor 103 on the basis of the power supplysignal.

Operations of the overload protective apparatus in accordance with thepresent invention will now be described in detail with the sameoperations as the conventional operation control device omitted sincethe present invention is about an overload protective apparatus and itsmethod capable of preventing damage of a compressor due to overload.

First, when a compressor 103 operates, the current detecting unit 102 ofthe overload protective apparatus detects a current applied to aninternal motor of the compressor in real time, and outputs the detectedcurrent value to the microcomputer 105.

When a current value detected by the current detecting unit 102 isgreater than a reference current value preset in the reference currentsetting unit 106, the microcomputer 105 generates a power cutoff signal,and outputs the generated power cutoff signal to the power supply unit101. But when a current value detected by the current detecting unit 102is the same as or smaller than a reference current value preset in thereference current setting unit 106, the microcomputer 105 generates apower supply signal, and outputs the generated power supply signal tothe power supply unit 101.

Thereafter, the triac (Tr1) of the power supply unit 101 cuts off powerapplied to an internal motor of the compressor 103 on the basis of thepower cutoff signal, or applies power to the internal motor of thecompressor 103 on the basis of the power supply signal. That is, thetriac (Tr1) of the power supply unit 101 controls a turn-on period onthe basis of the power supply signal or the power cutoff signaloutputted from the microcomputer 105, to cut off or pass power appliedto the internal motor of the compressor 103.

Hereinafter, a structure of a different embodiment of the overloadprotective apparatus of the reciprocating compressor in accordance withthe present invention will now be described in detail with reference toFIG. 3.

FIG. 3 is a block diagram showing a structure of a different embodimentof an overload protective apparatus of a reciprocating compressor inaccordance with the present invention.

As shown therein, an overload protective apparatus in accordance withthe different embodiment of the present invention includes: a referencecurrent setting unit 106 for pre-storing a reference current value; acurrent detecting unit 102 for detecting a current applied to aninternal motor (not shown) of the compressor when the compressor 103operates; a microcomputer 105 for generating a power cutoff signal whena current value detected by the current detecting unit 102 is greaterthan the reference current value stored in the reference current settingunit 106 and outputting the generated power cutoff signal, or forgenerating a power supply signal when the detected current value is thesame as or smaller than the reference current value and outputting thegenerated power supply signal; and switching unit 108 for cutting offpower applied to the internal motor of the compressor 103 on the basisof the power cutoff signal, or for applying power to the internal motorof the compressor 103 on the basis of the power supply signal.

In addition, the overload protective apparatus of the reciprocatingcompressor in accordance with the difference embodiment of the presentinvention further includes a comparing unit 107 which is drivenindependent of the microcomputer 105 when the microcomputer 105 does notoperate. That is, the comparing unit 107 compares a current valuedetected by the current detecting unit 102 and a reference current valuepre-stored in the reference current setting unit 106, generates a powercutoff signal when the current value detected by the current detectingunit 102 is greater than the reference current value and outputs thegenerated power cutoff signal to the switching unit 108. When thedetected current value is smaller than the reference current value, thecomparing unit 107 generates a power supply signal and outputs thegenerated power supply signal to the switching unit 108.

Herein, the microcomputer 105 receives the power supply signal from thecomparing unit 107 and controls a turn-on period of the triac (Tr1) inthe power supply unit 101 thereby applying power to the internal motorof the compressor, or the microcomputer 105 receives the power cutoffsignal from the comparing unit 107 and controls a turn-on period of theinternal triac of the power supply unit 101 thereby cutting off powerapplied to the internal motor of the compressor 103.

In addition, in the overload protective apparatus of the reciprocatingcompressor in accordance with the difference embodiment of the presentinvention, if the comparing unit 107 does not operate because of a breakdown or the like, the power can be cut off or applied by an outputsignal of the microcomputer 105. That is, in case that the comparingunit 107 does not operate, the microcomputer 105 generates a powercutoff signal when a current detected by the current detecting unit 102is greater than a reference current value pre-stored in the referencecurrent setting unit 106 and outputs the generated power cutoff signalto the switching unit 108. When the detected current value is smallerthan the reference current value, the microcomputer 105 generates apower supply signal and outputs the generated power supply signal to theswitching unit 108.

In the present invention, there may be used a device for performing acontact/noncontact type mechanical operation, such as a relay (notshown), as the switching unit 108, in order to apply or cut off powerapplied to an internal motor of the compressor 103 on the basis of anoutput signal of the microcomputer 105 or the comparing unit 107.

Hereinafter, operations of the overload protective apparatus of thereciprocating compressor in accordance with the difference embodiment ofthe present invention will now be described with reference to FIG. 4.

FIG. 4 is a flow chart showing an operational order of an overloadprotective apparatus of a reciprocating compressor in accordance withthe difference embodiment of the present invention.

First, the current detecting unit 102 detects a current applied to aninternal motor of the compressor 103 when the compressor 103 operates,in real time (S11).

The microcomputer 105 generates a power cutoff signal when a currentvalue detected by the current detecting unit 102 is greater than areference current value stored in the reference current setting unit102, and outputs the generated power cutoff signal to the switching unit108 (S12˜S14). At this time, the switching unit 108 cuts off powerapplied to the compressor on the basis of the power cutoff signal. Thatis, if over current is detected, the microcomputer 105 controls theswitching unit 108 such as a relay to cut off power applied to a motorin the compressor 103 (S15).

On the other hand, the microcomputer 105 generates a power supply signalwhen the detected current value is the same as or smaller than thereference current value and outputs the generated power supply signal tothe switching unit 108. At this time, the switching unit 108 appliespower to the compressor 103 on the basis of the power supply signal.That is, if over current is not detected, the microcomputer 105 controlsthe switching unit 108 such as a relay to apply power to the motor inthe compressor 103 and normally drives the compressor 103 (S16, S17).

In the overload protective apparatus of the reciprocating compressor inaccordance with the different embodiment of the present invention, ifthe microcomputer 105 does not operate due to a break down or the like,the power can be cut off or applied by an output signal of the comparingunit 107. That is, the comparing unit 107 compares a reference currentvalue pre-stored in the reference current setting unit 106 and a currentvalue detected by the current detecting unit 102, generates a powercutoff signal when the current value detected by the current detectingunit 102 is greater than the reference current value, and outputs thegenerated power cutoff signal to the switching unit 108 (S12˜S14). Atthis time, the switching unit 108 cuts off power applied to thecompressor 103 on the basis of the power cutoff signal.

On the other hand, when the detected current value is the same as orsmaller than the reference current value, the comparing unit 107generates a power supply signal, and outputs the generated power supplysignal to the switching unit 108. At this time, the switching unit 108applies power to the compressor on the basis of the switching signal.Herein, the reference current value is preset by a user and means acurrent value that should be applied to an internal motor of thecompressor 103 in order to normally drive the motor. That is, thereference current value is set in such a manner of measuring a currentvalue applied to an internal motor of the compressor when the compressornormally operates and storing the measured value (S12˜S13, 16).

The microcomputer 105 determines whether a predetermined time (e.g., 1˜3minutes) elapses after cutting off power applied to the compressor 103.If the predetermined time elapses, the microcomputer 105 generates thepower supply signal, and outputs the generated power supply signal tothe switching unit 108. At this time, the switching unit 108 appliespower to the compressor 103 on the basis of the power supply signal sothat the compressor 103 can normally operate.

On the other hand, if the predetermined time does not elapse, themicrocomputer 105 generates the power cutoff signal, and outputs thegenerated power cutoff signal to the switching unit 108. At this time,the switching unit 108 cuts off power applied to the compressor 103 onthe basis of the power cutoff signal (S18).

Accordingly, by using an operation control device for controlling anoperation of the compressor 103 without using an over load protector(OLP), damage of the compressor 103 due to overload can be prevented.

As so far described, the present invention is advantageous in thatdamage of a compressor due to the over current can be prevented withoutusing a conventional over load protector (OLP), by comparing a currentvalue applied to an internal motor of a compressor when the compressoroperates and the reference current value, and cutting off or applyingpower to the internal motor of the compressor on the basis of thecomparison result.

In addition, the present invention is advantageous in that a cost can bereduced by using an operation control device for controlling anoperation of the compressor, without using the conventional over loadprotector (OLP).

In addition, the present invention is advantageous in that thecompressor can be minimized by using an operation control device forcontrolling an operation of the compressor, without using theconventional over load protector (OLP).

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover modifications and variationsof this invention provided they come within the scope of the appendedclaims and their equivalents.

1. An overload protective apparatus of a compressor comprising: areference current setting unit for pre-setting a reference current valuefor normally operating a compressor; a current detecting unit fordetecting a current applied to the compressor; a comparing unitconnected to the current detecting unit, the comparing unit receiving adetected current value of the current applied to the compressor from thecurrent detecting unit and comparing the reference current value and thedetected current value, the comparing unit generating a first powercutoff signal when the detected current value during operation of thecompressor is greater than the reference current value and generating afirst power supply signal when the detected current value is smallerthan the reference current value; a microcomputer connected to thecurrent detecting unit, the microcomputer receiving the detected currentvalue of the current applied to the compressor from the currentdetecting unit and generating a second power cutoff signal when thedetected current value during the operation of the compressor is greaterthan the reference current value, and for generating a second powersupply signal when the detected current value is smaller than thereference current value, wherein the microcomputer receives the firstpower supply signal from the comparing unit and controls a turn-onperiod of a triac in a power supply unit to apply the power to aninternal motor of the compressor, or receives the first power cutoffsignal from the comparing unit and controls a turn-on period of aninternal triac of the power supply unit to cut off the power applied tothe internal motor of the compressor; and the power supply unitconnected to the comparing unit and the microcomputer for receiving thefirst and second power cutoff signals and the first and second powersupply signals, the power supply unit stopping supplying power to thecompressor in response to at least one of the first and second powercutoff signals, the power supply unit supplying the power to thecompressor in response to at least one of the first and second powersupply signals, wherein the power supply unit stops supplying power tothe compressor in response to either one of the first and second powercutoff signals, and the power supply unit supplies the power to thecompressor in response to either one of the first and second powersupply signals.
 2. The apparatus of claim 1, wherein the power supplyunit controls a turn-on period of an internal triac on the basis of thepower cutoff signal to cut off power applied to an internal motor of thecompressor, or controls a turn-on period of the internal triac on thebasis of the power supply signal to apply power to the internal motor ofthe compressor.
 3. The apparatus of claim 1, wherein the power supplyunit further comprises a relay, wherein the relay cuts off power appliedto the internal motor of the compressor on the basis of at least one ofthe first and second power cutoff signals or applies power to theinternal motor of the compressor on the basis of at least one of thefirst and second power supply signals.
 4. The apparatus of claim 1,wherein the power supply unit further comprises a device for performinga contact/noncontact type mechanical operation, wherein the device cutsoff power applied to the internal motor of the compressor on the basisof at least one of the first and second power cutoff signals, or appliespower to the internal motor of the compressor on the basis of at leastone of the first and second power supply signals.
 5. The apparatus ofclaim 1, wherein the power supply unit further comprises: an AC powersource; and a switching unit connected to the comparing unit and themicrocomputer for receiving the first and second power cutoff signalsand the first and second power supply signals, wherein the switchingunit, the internal triac, the compressor and the AC power source areconnected in series.
 6. An operation control device of a compressor,comprising: a voltage detecting unit for detecting a voltage applied toa compressor; a current detecting unit for detecting a current appliedto the compressor; a microcomputer connected to the current detectingunit, the microcomputer receiving a detected current value of thecurrent applied to the compressor from the current detecting unit andcalculating a stroke by using a voltage detected by the voltagedetecting unit and the detected current value detected by the currentdetecting unit, comparing the calculated stroke and a stroke referencevalue, and outputting a switching control signal on the basis of thecomparison result; a power supply unit for supplying a stroke voltage tothe compressor by on-off controlling AC power supplied to the compressoron the basis of the switching control signal outputted from themicrocomputer by using an internal triac; a reference current settingunit for presetting a reference current value of the compressor; acomparing unit connected to the current detecting unit, the comparingunit receiving the detected current value from the current detectingunit and comparing the reference current value and the detected currentvalue, the comparing unit generating a first power cutoff signal whenthe detected current value during the operation of the compressor isgreater than the reference current value and generating a first powersupply signal when the detected current value is smaller than thereference current value, the microcomputer generating a second powercutoff signal when the detected current value during operation of thecompressor is greater than the reference current value, themicrocomputer generating a second power supply signal when the detectedcurrent value is smaller than the reference current value, wherein themicrocomputer receives the first power supply signal from the comparingunit and controls a turn-on period of a triac in the power supply unitto apply the power to an internal motor of the compressor, or receivesthe first power cutoff signal from the comparing unit and controls aturn-on period of an internal triac of the power supply unit to cut offthe power applied to the internal motor of the compressor; and aswitching unit connected to the comparing unit and the microcomputer forreceiving the first and second power cutoff signals and the first andsecond power supply signals, the switching unit disconnecting the powersupply unit from an internal motor of the compressor in response to atleast one of the first and second power cutoff signals, the switchingunit connecting the power supply unit to the internal motor of thecompressor in response to at least one of the first and second powersupply signals, wherein the switching unit disconnects the power supplyunit from the internal motor of the compressor in response to either oneof the first and second power cutoff signals, and the switching unitconnects the power supply unit to the internal motor of the compressorin response to either one of the first and second power supply signals.7. The device of claim 6, wherein the switching unit, the internaltriac, the compressor and the AC power are connected in series.